1. Field of the Invention
The exemplary embodiments of the present invention relate to a method and system for detecting a coverage hole of a subscriber in a wireless cellular network.
2. Discussion of the Related Art
Generally, a position based service using a global position system (GPS) signal provides a service wanted by a user by measuring an accurate position within a region where a GPS signal is being received.
Such GPS system was first developed by the United States Department of Defense in the early 1970's and began its full-scale operation in the mid 1990's. The GPS system refers to a most ideal navigation system that can be used throughout the entire global region regardless of time and climate (or weather conditions). Although the GPS system was first developed for military purposes, due to its economic efficiency and usefulness, the GPS system has rapidly extended its field of usage for civilian usage, and the GPS system is currently known as the most generally used navigation system.
For example, diverse types of transportation vehicles, such as ships, airplanes, automobiles, and so on, are equipped with a GPS measurement device in order to verify the current position and travel speed or to decide a travel path. Such GPS location determination device receives radio waves indicating latitude, longitude, altitude, and so on, from 4 or more satellites located within 6 middle earth orbits, thereby being capable of calculating (or computing) the current position of the corresponding transportation vehicle.
However, since such GPS measurement device is capable of performing location measurement only in regions where signals can be received from the satellites, when the vehicle enters an indoor or outdoor coverage hole (or shadow area), such as the inside of a building or a tunnel, where GPS signals cannot be received, it is impossible to perform position search by using the GPS signal.
Therefore, the method of receiving a GPS signal and outputting a current position within an installed electronic map is disadvantageous in that it cannot be used in a coverage hole, where the GPS signal cannot be received.
In order to resolve the above-described problems, a technology for estimating the position (or location) of a subscriber even in a coverage hole, where GPS signals cannot be received, is currently under active research and development.
For example, in the Korean Patent Application No. 10-2011-0005394 (published on Jan. 18, 2001), a geographical information search technology, which can determine current positions by using global coordinates even in coverage holes, by determining a correlation between a Global Coordinate, at which a GPS signal is received, and a Local Coordinate respective to the inside of a building or an outdoor coverage hole, where GPS signals cannot be received, and by converting a local coordinate inside of a building to a global coordinate based upon the determined correlation, is disclosed.
Since the conventional position information detection technology indirectly estimates the position of a subscriber user equipment (UE) by using a triangulation method using GPS information, the information within the coverage hole is unreliable, and, therefore, an additional position detection technology or management server, such as WiFi or GPS, is being required.